Turk J Chem

(2015) 39: 1232 – 1246

c⃝ TÜBİTAKdoi:10.3906/kim-1506-32

Turkish Journal of Chemistry

http :// journa l s . tub i tak .gov . t r/chem/

Research Article

Efficient C–C cross-coupling reactions by (isatin)-Schiff base functionalized

magnetic nanoparticle-supported Cu(II) acetate as a magnetically recoverable

catalyst

Seyedeh Simin MIRI1, Mehdi KHOOBI2,3, Fatemeh ASHOURI4, Farnaz JAFARPOUR1,Parviz RASHIDI RANJBAR1, Abbas SHAFIEE2,∗

1School of Chemistry, College of Science, University of Tehran, Tehran, Iran2Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center,

Tehran University of Medical Sciences, Tehran, Iran3Medical Biomaterials Research Center, Tehran University of Medical Sciences, Tehran, Iran

4Department of Applied Chemistry, Faculty of Pharmaceutical Chemistry, Pharmaceutical Sciences Branch,Islamic Azad University, Tehran, Iran

Received: 14.06.2015 • Accepted/Published Online: 07.09.2015 • Printed: 25.12.2015

Abstract: Copper catalysts were simply fabricated through surface modification of superparamagnetic iron nanopar-

ticles with indoline-2,3-dione(isatin)-Schiff-base and interaction with Cu from low-cost commercially available starting

materials. Catalysts were characterized using atomic absorption spectrophotometry, Fourier transform infrared spec-

troscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, UV/Vis spectroscopy, scanning

electron microscopy, and transmission electron microscopy. These catalysts showed high efficiency for phosphine-free

Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions with good diversity and generality. The catalysts could be

easily recovered and reused several times without a significant loss in their catalytic activity and stability.

Key words: Copper, coupling, magnetic nanoparticles, catalyst, Schiff base

1. Introduction

C–C bond formation is one of the most commonly employed chemical transformations generally used in both

academic1 and industrial chemistry.2 Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions are the most

widely used methods for extensive production of key intermediates during preparation of natural,3 nonnatural,4

and bioactive compounds.5,6 Although homogeneous palladium complexes as conventional catalysts in cross-

coupling reactions have shown high reaction rates, suitable turnover numbers, and sometimes perfect selectivity

and yield, these types of catalysts suffer from the problem of recycling of the catalyst as well as instability

during reaction at high temperatures.7,8 Recoverability and reusability of the catalyst are a challenge from

environmental and economic points of view, especially when precious metal catalysts are used. In this regard,

magnetic nanoparticles (MNPs) can particularly meet this challenge due to their ability to easily separate

from liquid reaction media by an external magnetic field. Among various MNPs, magnetite (Fe3O4) has

attracted considerable interest and has applications in various fields due to its large surface-to-volume ratio,

biocompatibility, nontoxicity, ease of synthesis, and surface functionalization.9,10

∗Correspondence: shafieea@tums.ac.ir

1232

MIRI et al./Turk J Chem

In addition, the type of ligand in transition metal cross-coupling is one of the pivotal factors determining

catalytic performance. Conventionally, homogeneous palladium/phosphine complexes were used in Mizoroki–

Heck and Suzuki–Miyaura reactions. However, limiting aspects of palladium catalysts like high cost and toxicity

have limited their immense applications on industrial scales.11 In recent years, copper catalytic systems have

been attracting more attention because of their low costs, biocompatibility, and increased catalytic ability in

comparison with palladium and other frequently used systems for catalyzing cross-coupling reactions.12−14

Since ligands can influence the selectivity and reactivity of transformations, careful choice of ligand is

required for functionalization of catalyst supports.15−21 Among the various applied ligands, nitrogen-containing

ligands and especially Schiff bases as potent organic ligands in coordination chemistry play an important role

in tuning the electronic properties of metal ions in complexes.22

Since isatin-based Schiff base ligands have shown variable denticities toward several metal ions,23,24

we were encouraged to fabricate a new magnetic copper Schiff base complex via surface modification of

superparamagnetic iron nanoparticles with an indoline-2,3-dione (isatin)-Schiff base and subsequent ligand

coordination with Cu (Scheme).

Scheme. The consecutive steps for preparing copper catalyst.

2. Results and discussion

2.1. Catalyst preparation and characterization

The sequential steps for stabilizing Cu(II) ions by indoline-2,3-dione (isatin)-Schiff base containing MNPs is

shown in the Scheme. Condensation reaction of Fe3O4@SiO2 –NH2 with isatin (Isa) was used to produce

a suitable interaction capacity of N–O Schiff base and metal species. An inductive coupled plasma-atomic

emission spectrometry (ICP) analyzer was used to determine the content of Cu and revealed the presence of

0.17 mmol/g. Fourier transform infrared (FT-IR) analysis was used to confirm the modification of the magnetite

1233

MIRI et al./Turk J Chem

surface with functional groups and also metal anchoring on the nanocomposite. The FT-IR spectra of Fe3O4 ,

Fe3O4@SiO2–NH2 , Fe3O4@SiO2–Isa, and Fe3O4@SiO2–Isa Cu(II) are shown in Figure 1. The absorption

band at 584–633 cm−1 in the MNPs is attributed to the stretching vibration of Fe–O, and the peak at 3415

cm−1 is assigned to the stretching vibrations of Fe–OH groups on the surface of the MNPs. The strong broad

band at 1000–1100 cm−1 corresponds to the stretching vibration of the Si–O–Si group and confirmed the silica

coating on the surface of Fe3O4 . The bands at 2940 and 1446 cm−1 could be ascribed to the stretching

vibrations of C–H and C–N bonds, respectively (Figure 1, line b). After condensation of isatin with amine

groups of Fe3O4@SiO2–NH2 , more peaks appeared at 1714 and 1621 cm−1 , which are due to the stretching

vibration of carbonyl and C=N bands, respectively. The FT-IR spectrum of the Cu(II) catalyst shows a red

shift in the carbonyl bond at a lower frequency (1708 cm−1) in comparison with the band for Fe3O4@SiO2 –Isa.

The stretching bands correspond to the carbonyl and C=N bonds of complexes show a red shift compared with

the Schiff base (Fe3O4@SiO2–Isa) and appear at a lower frequency (Figure 1, line c in comparison with line

d). This could be attributed to the coordination of the carbonyl and C=N bands with copper ions.25,26

Figure 1. FT-IR spectra of (a) Fe3 O4 , (b) Fe3 O4 @SiO2 –NH2 , (c) Fe3 O4 @SiO2 –Isa, and (d) Fe3 O4 @SiO2 –Isa

Cu(II).

The thermogravimetric analysis (TGA) curves of Fe3O4 , Fe3O4@SiO2–Isa, and copper catalyst are

shown in Figure 2. Weight loss observed during heating from 50 to 200 ◦C could be ascribed to the loss

of physisorbed water and other solvents on the particles during nanocatalyst procurement (Figure 2, line a).

Thermal decomposition of the immobilized Schiff base and corresponding complexes revealed the continuous

weight loss of organic moiety absorbed on the particle surface in the temperature range of 200–600 ◦C. As

illustrated in Figure 2 (line b), the amount of Schiff base ligand loading on the surface of the MNPs is

approximately 8%. As a result, the nanocatalyst is stable up to at least 200 ◦C.

The X-ray powder diffraction (XRD) patterns of naked Fe3O4 and catalyst are shown in Figure 3. The

XRD results showed that diffraction peaks at 2θ of 30.09◦ , 35.7◦ , 43.3◦ , 53.85◦ , 57.31◦ , and 62.97◦ correlated

to diffraction of (220), (311), (400), (422), (511), and (440) of the Fe3O4 nanoparticles were found in all samples.

Therefore, the multiple steps of catalyst preparation did not change the crystal structure of the Fe3O4 cores.

1234

MIRI et al./Turk J Chem

The new peaks at 2θ = 40.33◦ , 59.57◦ , and 66.19◦ corresponding to the (111), (202), and (311) planes of

Cu+2 indicated the existence of Cu+2 in the catalyst.27 The broad peak that appeared at 2θ = 21–25◦ in

both catalysts is related to the amorphous silica shell on the surface of the MNPs28 The average crystallite

sizes of MNPs were estimated as 13.5 nm using the Scherrer equation.

Figure 2. TGA curves of (a) Fe3 O4 , (b) Fe3 O4 @SiO2 –Isa, and (c) Fe3 O4 @SiO2 –Isa Cu(II) catalyst.

Diffuse reflectance spectroscopy (DRS) was used for corroboration of oxidation states of Cu species in the

structure. The spectrum of Fe3O4@SiO2–Isa Cu(II) shows higher absorption at ∼700–800 nm compared toFe3O4@SiO2–Isa, which can be assigned to the Cu(II) d–d transition intensity in the presence of Fe3O4@SiO2 –

Isa Cu(II) (Figure 4).29−32 The Fe3O4@SiO2 –Isa Cu(II) and Fe3O4@SiO2 –Isa indicated a peak at 220 nm,

which can be attributed to the existence of the magnetic core.

0

1

2

3

4

5

6

7

8

9

10

200 400 600 800 1000 1200 1400 1600

Ab

sorp

tio

n (

a.u

.)

Wavelength (nm)

a

b

Figure 3. XRD pattern of (a) Fe3 O4 and (b)

Fe3 O4 @SiO2 –Isa Cu(II) catalyst.

Figure 4. DRS pattern of Fe3 O4 @SiO2 –Isa Cu(II) cat-

alyst (a) and Fe3 O4 @SiO2 –Isa (b).

The magnetic feature of Fe3O4 MNPs and Fe3O4@SiO2 –Isa was measured with a VSM (vibrating

sample magnetometry) instrument (Figure 5, lines a and b, respectively). Base on the hysteresis loop, magnetic

1235

MIRI et al./Turk J Chem

saturation of Fe3O4 MNPs and Fe3O4@SiO2 –Isa is 46.5 and 37.5 emu g−1 , respectively. The decrease in

mass saturation magnetization of Fe3O4@SiO2–Isa could be ascribed to the nonmagnetic silica and organic

moieties. Although the σs values of the Fe3O4@SiO2 –Isa are decreased, the superparamagnetic properties

of nanoparticles have been still been preserved and the absence of remanence magnetization and coercivity

confirm this. The catalyst could be efficiently isolated magnetically from the solution and reused for several

runs (Figure 5).

Figure 5. VSM curve of Fe3 O4 MNPs (a) and Fe3 O4 @SiO2 –Isa (b); reaction mixture (c) and isolation of catalyst by

external magnet (d).

The SEM and TEM images of the catalysts are presented in Figures 6a–6c. According to these images,

most of particles have a narrow size distribution (the inset histogram of Figure 6c) with quasi-spherical shape.

The mean diameter of the nanoparticles was about 12 nm. These results are consistent with the average

crystallite sizes estimated from XRD by using Scherrer’s equation. Energy dispersive X-ray spectroscopy (EDS)

spectra were also used to determine the elemental composition of catalysts. EDS spectra of Fe3O4@SiO2 –Isa

Cu(II) clearly demonstrate the presence of Cu, Fe, and Si as well as other elements attributed to the organic

moiety. The presence of these signals confirms the successful preparation of catalyst and copper loading (Figure

6d).

2.2. Catalytic activity of catalysts in Mizoroki–Heck coupling reaction

The catalytic activity of the as-prepared Cu catalysts was investigated in Mizoroki–Heck coupling reactions. As

a model reaction, the coupling of iodobenzene and methyl acrylate was screened in order to find the optimized

conditions (Table 1). A careful view into the C–C cross-coupling reaction process indicates that the reaction

conditions have affected the yield of the Mizoroki–Heck reaction.33,34 The influence of different experimental

parameters, such as reaction time and amount of catalyst and base, were also optimized in the model reaction.

Among them, the best condition was obtained in the presence of Et3N as base and DMF as solvent (Table 1,

entry 8). Using Cs2CO3 as a strong base caused a decrease in the yield of the desirable stilbene due to the

1236

MIRI et al./Turk J Chem

formation of homocoupling products (Table 1, entry 4).35 The results showed that 1,4-dioxane and MNPs are

also effective (Table 1, entries 10 and 14). The same results were also obtained when the amount of the catalyst

was decreased to 0.33 mol% and temperature was decreased to 80 ◦C (Table 1, entry 18). It was noted that,

as expected, temperature had a noteworthy effect on the effectiveness of the present catalytic system.

Figure 6. SEM images of Fe3 O4 (a) and Fe3 O4 @SiO2 –Isa Cu(II) (b); TEM image and particle size distribution

histogram of Fe3 O4 @SiO2 –Isa Cu(II) catalyst (particle size: 12 nm) (c); and EDS of Fe3 O4 @SiO2 –Isa Cu(II) catalyst

(d).

Because good yield of the product was acquired at 100 ◦C, a variety of iodobenzenes and alkenes

including either aromatic or aliphatic alkenes with electron-donating or electron-withdrawing substitution were

1237

MIRI et al./Turk J Chem

investigated under the optimized reaction conditions (100 ◦C). It was observed that the system for the coupling

reaction of aryl halides with alkenes can be adopted for the catalytic active and regioselective coupling (Table 2).

Table 1. Optimization of reaction condition for Heck coupling reaction of methylacrylate with iodobenzene in the

presence of Fe3 O4 @SiO2 –Isa Cu(II) catalyst.a

O

O

O

OI

Entry Base Solvent Conversion (%)b

1 Na2CO3 DMF 912 KH2PO4 DMF 503 Na2HPO4 DMF 304 Cs2CO3 DMF Trace5 NaOAc DMF -6 DABCO DMF -7 K2CO3 DMF 988 NEt3 DMF 1009 (CH3)3COK DMF -10 NEt3 NMP 10011 NEt3 DMF 10012 NEt3 PEG 8013 NEt3 EtOH 8014 NEt3 1,4-Dioxane 10015 NEt3 Mesitylene Trace16 NEt3 Ethylene glycol Tracec17 NEt3 DMF 100d18 NEt3 DMF 90e19 NEt3 DMF 100

a Reaction conditions: iodobenzene (1.0 mmol), methylacrylate (1.1 mmol), base (2.0 mmol), solvent (5.0 mL), 120 ◦ C,

12 h, copper catalyst (0.82 %mol); b Checked by GC analysis; c Copper catalyst (0.33 %mol), 100 ◦ C; d Copper catalyst

(0.33 %mol), 80 ◦ C; e 100 ◦ C, 8 h.

2.3. Catalytic activity of the copper catalyst in Suzuki–Miyaura coupling reaction

The efficiency of the Fe3O4@SiO2 –Isa Cu(II) catalyst in Mizoroki–Heck coupling reaction led us to study the

potential of this catalyst in the Suzuki–Miyaura cross-coupling reactions of aryl halides and arylboronic acids.

In order to optimize the reaction condition, coupling of 4-iodotoluene and 4-methoxyphenylboronic acid was

selected as the model reaction. Influence of different bases and solvents as well as the amount of the catalyst,

temperature, and time of the reaction were also investigated. The results showed that the model reaction can

be promoted in NMP and DMF with high yield (Table 3, entries 1 and 2). Due to the importance of green

solvent application in organic reactions, we examined the performance of ethanol as a green solvent in the

model reaction. Fortunately, excellent yield was obtained in the presence of K2CO3 as the base in ethanol

solvent (Table 3, entry 3). However, addition of water slightly declined the yield of the reaction in comparison

with ethanol. The effects of different bases such as NEt3 , DABCO (1,4-diazabicyclo[2.2.2]octane), KH2PO4 ,

1238

MIRI et al./Turk J Chem

Table 2. The copper catalyzed Mizoroki–Heck coupling reactions of various aryl iodides with terminal alkenes.a

I

R2R2

R1R1

Entry Aryl iodide Product Time (h) Conversionb (%) Selectivityb (%)

1

I

12 90 86

2 MeI Me

12 96 90

3MeO

IOMe

15 65 75

4

I

MeMe

12 97 90

5

I

OMe

OMe

15 78 95

6F3C

ICF3

8

91

100

7

I

OO

8 100 50

8

I

O

O

O

O 8 100 100

9

I

O

O(n-Bu)

O

O

(CH2)3CH3

8 76 80

10

I

CNNC

8 100 90

11

I

O(n-dedecyl)

O

O

O

(CH2)9CH3

8 90 90

12

Br

Me

O

OO

O

8 72 90

13

Br

Me Me

12 55 70

a Reaction conditions: the reactions were done in the present of copper catalyst (0.33 mol%) in the coupling reaction of

aryl iodide (1.0 mmol), alkene (1.1 mmol), and NEt3 (2.0 mmol) in DMF (5.0 mL) at 100◦ C in a sealed tube; b GC

conversion.

1239

MIRI et al./Turk J Chem

(CH3)3COK, and Na2CO3 were also studied. The best result was obtained by 0.33 mol% copper catalyst in

the presence of K2CO3 in ethanol at 70◦C for 5h (Table 3, entry 11). Changing the amount of catalyst and

temperature did not show meaningful improvement in the yield of the reaction.

Table 3. Optimization of effective factors in Suzuki–Miyaura cross-coupling reaction catalyzed by immobilized copper

complex.a

OMeMe

Me

IB(OH)2

Me O

Cu comple x

Entry Solvent Base Time (h) Conversionb (%)1 DMF K2CO3 12 922 NMP K2CO3 12 903 EtOH K2CO3 12 944 EtOH KH2PO4 12 Trace5 EtOH (CH3)3COK 12 756 EtOH Na2CO3 12 907 EtOH NEt3 12 Trace8 EtOH DABCO 12 759 EtOH:H2O (1:1) K2CO3 12 5510 EtOH K2CO3 5 9411 EtOH K2CO3 5 94

c

a Reaction conditions: 4-iodotoluene (1.0 mmol), 4-methoxyphenylboronic acid (1.2 mmol), base (2.0 mmol), solvent (5

mL), Fe3 O4 @SiO2 –Isa Cu(II) catalyst (0.82 mol%), 70◦ C in a sealed tube; b Determined by GC; c Copper catalyst

0.33 mol%.

The couplings between various aryl halides and arylboronic acids were investigated. As indicated in Table

4, good to excellent yields were obtained for various substrates. The reaction progressed reasonably well with

bromobenzene to afford the stilbene in good yield (70%) (Table 4, entry 2). Thus, the Fe3O4@SiO2 –Isa Cu(II)

catalyst is efficient for Suzuki–Miyaura cross-coupling reaction.

To evaluate the efficiency and stability of the catalysts during several runs, our study was concentrated on

the recyclability and reusability of these catalysts. After each catalytic run, catalysts were easily recovered by

a magnetic field, washed repeatedly with aqueous methanol, and dried under a vacuum at 50 ◦C to be checked

in the next run. Leaching tests after each catalytic run in iodobenzene and methylacrylate coupling as a model

reaction under optimized conditions revealed that the amount of Cu leached from the heterogeneous catalyst

was negligible (less than 0.2 ppm) as determined by ICP-AES of the clear filtrate. This result shows that there

is no contribution from homogeneous catalysis of active Cu species leaching into the reaction solution.

A hot filtration test was also conducted to confirm that the reaction was indeed catalyzed by Cu

heterogeneous catalyst instead of free Cu. After the first catalytic reaction, the catalyst was simply separated

from the reaction mixture by an external magnet. The fresh reagents were then added to the filtrated solution.

The resulting mixture was stirred at 100 ◦C. The conversion was negligible after adequate time (8 h). These

results confirmed that the coupling reaction could only proceed in the presence of the solid catalyst, and there

was no contribution from leached Cu species in the liquid phase.

Efforts were directed toward the study of recycling of such catalytic systems using the Mizoroki–Heck

reaction of iodobenzene with methyl acrylate. The supported catalysts were recovered by a magnetic field

1240

MIRI et al./Turk J Chem

Table 4. The Suzuki–Miyaura cross-coupling reactions of aryl halides with phenylboronic acids in the present ofFe3 O4 @SiO2 –Isa Cu(II) catalyst.

a

X +

(HO)2B

R2R1

X:Br, I

R1 R2

Cu complex

R1

R2

Aryl halide Product Conversionb (%)

1 4-Me 4-OMe Br OMe 35

2 H 4-OMe Br MeO 70

3 H 4-OMe I MeO 99

4 4-Me 3-NO2

I

NO2

91

5 4-OMe 4-OMe I MeO OMe 99

6 2-Me 4-OMe IMeO

94

7 2-CF3

4-OMe IMeO

F3C

85

8 2-Me 4-OMe BrMeO

40

9 4-OMe H I MeO 92

10 2-OMe H I

OMe

85

11 2-OMe 4-OMe IMeO

MeO

99

12 4-Me 4-OMe I MeO 94

a Reaction conditions: aryl halide (1.0 mmol), phenyl borinic acid (1.2 mmol), K2 CO3 (2.0 mmol), Cu catalyst (0.33

mol%), EtOH (5 mL), 70 ◦ C, 5 h; b Determined by GC.

1241

MIRI et al./Turk J Chem

for the next reaction, washed with aqueous methanol, and dried under vacuum at 50 ◦C to reactivate the

catalysts for the next run. The model reaction under the optimized conditions mentioned above was run for

five consecutive cycles repeating the regeneration process of two catalysts. There was a drop in the yield of

the reaction catalyzed by copper catalyst after the fourth cycle, which could be attributed to the leaching of

copper ions (Figure 7). ICP analysis result showed 6% deterioration of copper content at the fifth cycle. Lower

stability of copper catalyst for Suzuki–Miyaura reaction may be attributed to the metal leaching due to the

effect of protic solvent and high temperature of the reaction media.36

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5

Co

nve

rsio

n (

%)

Run

Mizoroki - Heck reaction Suzuki - Miyaura reaction

Figure 7. Recovery of Fe3 O4 @SiO2 –Isa Cu(II) catalyst in Heck and Suzuki coupling reactions.

Considering published reports in this field, it has been revealed that some heterogeneous copper-catalyzed

cross-coupling reactions suffer from elevated temperature to obtain desirable results (Table 5, entries 2–4),12,37,38

low yield under the optimum conditions,39 or costly and difficult procedures40,41 for catalyst preparation (Table

5, entry 5, and Table 6, entry 2). In this study, not only was an efficient hybrid magnetic copper catalyst

conveniently prepared for the C–C cross-coupling reactions with a low level of the catalyst, but it also gave the

desired products in moderate to excellent yields without using bimetallic systems (Table 5, entry 6, and Table

6, entries 4–6).42−44

Table 5. Comparison of catalytic activity of various heterogeneous catalysts in the Mizoroki–Heck cross-coupling

reactions.

I

R2R2

R1R1

Entry R1 R2 CatalystTemperature Yield (%)/

Ref.(◦C) Time (h)

1 H Ph Fe3O4@SiO2–Isa Cu(II) 100 90a/8 This work

2 H COOBu Copper bronze 130 70/24 124 H Ph Si-NH2-Cu(OAc)2 150 40/48 373 OMe Ph Cu/Al2O3 150 70/48 385 H COOBu Cu/PrePAN fiber mats 130 99/40 406 H Ph Pd/Cu (4:1) bimetallic NPs 100 91/18 42aConversion.

1242

MIRI et al./Turk J Chem

In summary, we have presented a simple procedure for preparing a magnetically recoverable copper

catalyst with high efficiency for Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions with low price

for industrial applications. The catalyst showed good diversity and generality in both reactions. This method

requires remarkably small amounts of catalyst without any activator or any toxic ligand. The superparamagnetic

nature of the catalyst provides its easy isolation and reuse. In addition, high activity and selectivity, easy

separation of catalysts, and good performance in the recycling reaction are the valuable advantages of this

Fe3O4@SiO2–Isa Cu(II) catalyst.

Table 6. Comparison of the catalytic activity of various heterogeneous catalysts in the Suzuki–Miyaura cross-coupling

reaction.

I B(OH)2

Entry Catalyst Temperature (◦C) Yield (%) Ref.1 Fe3O4@SiO2–Isa Cu(II) 70 92

a This work2 Cu nanocolloid 110 62 393 3D MOF{[Cu(4-

tba)2](solvent)} n25 88 41

4 Cu-Pd bimetallic cata-lysts supported on 4Åmolecular sieve

78 > 99 43

5 Cu, monometallic cata-lysts supported on 4Åmolecular sieve

78 62a 43

6 Pd-Cu/C 78 97.5 44aConversion.

3. Experimental

3-Aminopropyltriethoxysilane (APTES), tetraethyl orthosilicate (TEOS), isatin (Isa), and other chemicals and

solvents were purchased from Merck and used as received without further purification. Deionized water was

used throughout the experiments. All solvents were of analytical grade. TEM images were carried out using a

Philips EM208 at 100 kV. Metal existence, phase purity, and crystallinity of the sample were characterized by

XRD using a Philips X’Pert MPD with Cu Kα radiation. The UV-DRS of samples was recorded with a PE

Lambda 20 spectrometer. FT-IR spectra were obtained using a Bruker Equinox 55 spectrophotometer. ICP

was conducted on a Vista-MPX (Varian) for content determination of copper on supports. Conversion % was

determined by GC on a Shimadzu model GC-14A instrument. TGA results were obtained by TA Q50 V6.3.

SEM images were carried out on a Hitachi S-4160. EDS data were recorded on a VEGA3 XMU. Magnetic

properties of modified MNPs were studied by VSM (Meghnatis Kavir Kashan Co., Kashan, Iran).

3.1. Catalyst preparation

Preparation of Fe3O4 nanoparticles: Fe3O4MNPs were prepared via the chemical coprecipitation method.45

An aqueous solution (100 mL) of FeCl2 .4H2O (1.0 g, 5.0 mmol) and FeCl3 .6H2O (2.6 g, 9.6 mmol) was mixed

under nitrogen atmosphere with vigorous stirring, and then NH4OH (10 mL of 25 wt%, excess) was added

dropwise to the solution. The solution was heated to 70 ◦C and kept at this temperature for 2 h. The resultant

black dispersion was cooled and separated from the solution with a permanent magnet and washed several times

1243

MIRI et al./Turk J Chem

with deionized water and ethanol until the pH value held at 7. The precipitate was dried in a vacuum oven at

80 ◦C for 24 h.

Preparation of Fe3O4@SiO2 nanoparticles: Fe3O4 MNPs (0.7 g) were dispersed in a mixture of ethanol

(40 mL) and deionized water (10 mL). To this dispersion, TEOS (0.3 mL) and NH4OH (0.6 mL) were added

and the mixture was stirred vigorously at room temperature for 12 h. Silica-coated MNPs were magnetically

isolated by a permanent magnet, repeatedly washed with ethanol and deionized water, and finally dried in a

vacuum at 50 ◦C for 24 h.46

General procedure for preparation of amine functionalized MNPs (Fe3O4@SiO2–NH2) : presynthesized

Fe3O4@SiO2 MNPs (1.0 g) were well dispersed in anhydrous toluene and then an excess amount of 3-

aminopropyltriethoxysilane (0.7 mL, 0.66 g) was added dropwise to this dispersion. The mixture was refluxed

for 24 h under argon protection. The resulting amine functionalized MNPs were magnetically separated by

external magnet, washed with methanol and acetone several times, and dried in a vacuum oven at 50 ◦C

overnight.47

Preparation of isatin functionalized MNPs (Fe3O4@SiO2–Isa): the appropriate Schiff base was prepared

by condensation reaction of Fe3O4@SiO2–NH2 with isatin. The solution of isatin (10 mmol) in ethanol (25

mL) was added dropwise to the dispersed Fe3O4@SiO2 –NH2 nanoparticles (1.0 g) in ethanol (25 mL). The

resulting mixture was refluxed under argon atmosphere for 24 h. The product was collected by an external

magnet and carefully washed with ethanol. Subsequently, it was treated by Soxhlet extraction with ethanol for

24 h to remove unreacted substrates and byproducts and finally dried at 50 ◦C overnight in a vacuum oven.

Preparation of copper loading on Fe3O4@SiO2 –Isa MNPs (Fe3O4@SiO2–Isa Cu(II)): the immobilized

Schiff base (300 mg) and copper acetate (0.6 mmol) were dispersed in acetonitrile (80 mL) under sonication for

30 min. The mixture was stirred vigorously for 24 h under argon at room temperature. The magnetic catalyst

was washed with acetone, ethanol, and water several times and dried under a vacuum at room temperature to

yield the immobilized copper Schiff base complex.

3.2. General procedure for Heck coupling reaction

A mixture of aryl iodide (1.0 mmol), methyl acrylate (1.1 mmol), triethylamine (2.0 mmol), and an adequate

amount of copper catalyst (0.33 mol%) was taken in a round-bottom flask and stirred in DMF (5.0 mL) at

100 ◦C, and the progress of the reaction was monitored by GC.48 At the end of the reaction, the mixture was

cooled to room temperature and the catalyst was isolated by magnetic decantation. The recovered catalyst

was thoroughly rinsed with ethyl acetate and distilled water, dried at room temperature, and used without

any pretreatment for the next runs. The recyclability of the catalyst was screened in the reaction between

iodobenzene and methyl acrylate according to the above procedure.

3.3. General procedure for Suzuki coupling reaction

The mixture of aryl iodide (1.0 mmol), phenyl boronic acid (1.1 mmol), potassium carbonate (2.0 mmol), and

copper catalyst (0.33 mol%) was taken in a round-bottom flask and stirred in ethanol (5.0 mL) under reflux

conditions (70 ◦C), and the progress of the reaction was monitored by GC.49 At the end of the reaction, the

mixture was cooled to room temperature and the solid catalyst was isolated by magnetic decantation. The

recyclability of the catalyst was screened in the reaction between iodoanisole and phenylboronic acid according

to the same method described above.

1244

MIRI et al./Turk J Chem

Acknowledgment

This work was supported by grants from the Research Council of Tehran University of Medical Science.

References

1. Trzeciak, A. M.; Zió lkowski, J. J. Coord. Chem. Rev. 2005, 249, 2308–2322.

2. Farina, V. Adv. Synth. Catal. 2004, 346, 1553–1582.

3. Mizutani, T.; Honzawa, S.; Tosaki, S. Y.; Shibasaki, M. Angew. Chem. Int. Ed. 2002, 41, 4680–4682.

4. Dı́ez-González, S.; Nolan, S. P. Top. Organomet. Chem. 2007, 21, 47–82.

5. Choudary, B. M.; Madhi, S.; Chowdari, N. S.; Kantam, M. L.; Sreedhar, B. J. Am. Chem. Soc. 2002, 124, 14127–

14136.

6. Häberli, A.; Leumann, C. J. Org. Lett. 2001, 3, 489–492.

7. Makhubela, B. C.; Jardine, A.; Smith, G. S. Appl. Catal. A-Gen. 2011, 393, 231–241.

8. Iranpoor, N.; Firouzabadi, H.; Motevalli, S.; Talebi, M. J. Organomet. Chem. 2012, 708, 118–124.

9. Yuan, D.; Zhang, Q.; Dou, J. Catal. Commun. 2010, 11, 606–610.

10. Costa, N. J.; Kiyohara, P. K.; Monteiro, A. L.; Coppel, Y.; Philippot, K.; Rossi, L. M. J. Catal. 2010, 76, 382–389.

11. Mao, J.; Guo, J.; Fang, F.; Ji, S. J. Tetrahedron 2008, 64, 3905–3911.

12. Calò, V.; Nacci, A.; Monopoli, A.; Ieva, E.; Cioffi, N. Org. Lett. 2005, 7, 617–620.

13. Liu, Y.; Li, D.; Park, C. M. Angew. Che. Int. Ed. 2011, 50, 7333–7336.

14. Gigant, N.; Gillaizeau, I. Org. Lett. 2012, 14, 3304–3307.

15. Ko, S.; Jang, J. Angew. Chem. Int. Ed. 2006, 45, 7564–7567.

16. Cui, J.; He, T.; Zhang, X. Catal. Commun. 2013, 40, 66–70.

17. Phan, N. T.; Le, H. V. J. Mol. Catal. A-Chem. 2011, 334, 130–138.

18. Zamani, F.; Hosseini, S. M. Catal. Commun. 2014, 43, 164–168.

19. Beygzadeh, M.; Alizadeh, A.; Khodaei, M.; Kordestani, D. Catal. Commun. 2013, 32, 86–91.

20. Dehghani, F.; Sardarian, A. R.; Esmaeilpour, M. J. Organomet. Chem. 2013, 743, 233–240.

21. Taher, A.; Kim, J. B.; Jung, J. Y.; Ahn, W. S.; Jin, M. J. Synlett 2009, 15, 2477–2482.

22. Tamizh, M. M.; Karvembu, R. Inorg. Chem. Commun. 2012, 25, 30–34.

23. Monier, M.; Ayad, D.; Wei, Y.; Sarhan, A. J. Hazard. Mater. 2010, 177, 962–970.

24. Lagasi, M.; Moggi, P. J. Mol. Catal. A-Chem. 2002, 183, 61–72.

25. Zhu, M.; Diao, G. J. Phys. Chem. C 2011, 115, 24743–24749.

26. Deng, Y.; Qi, D.; Deng, C.; Zhang, X.; Zhao, D. J. Am. Chem. Soc. 2008, 130, 28–29.

27. Wang, B.; Wu, X. L.; Shu, C. Y.; Guo, Y. G.; Wang, C. R. J. Mat. Chem. 2010, 20, 10661–10664.

28. Qadir, M.; Möchel, T.; Hii, K. K. Tetrahedron 2000, 56, 7975–7979.

29. Zhang, M.; Shao, C.; Guo, Z.; Zhang, Z.; Mu, J.; Cao, T.; Liu, Y. ACS Appl. Mater. Interfaces 2011, 3, 369–377.

30. Irie, H.; Miura, S.; Kamiya, K.; Hashimoto, K. Chem. Phys. Lett. 2008, 457, 202–205.

31. Lee, S. S.; Bai, H.; Liu, Z.; Sun, D. D. Water Res. 2013, 47, 4059–4073.

32. Arifin, S. A.; Jalaludin, S.; Djaja, N. F.; Saleh, R. Adv. Mater. Res. 2015, 1112, 221–227.

33. Bagherzadeh, M.; Ashouri, F.; Hashemi, L.; Morsali, A. Inorg. Chem. Commun. 2014, 44, 10–14.

34. Amini, M.; Bagherzadeh, M.; Rostamnia, S. Chin. Chem. Lett. 2013, 24, 433–436.

35. Wu, Q.; Wang, L. Synthesis 2008, 2008, 2007–2012.

1245

http://dx.doi.org/10.1016/j.ccr.2005.02.001http://dx.doi.org/10.1002/adsc.200404178http://dx.doi.org/10.1002/anie.200290014http://dx.doi.org/10.1021/ja026975whttp://dx.doi.org/10.1021/ja026975whttp://dx.doi.org/10.1021/ol007029shttp://dx.doi.org/10.1016/j.apcata.2010.12.002http://dx.doi.org/10.1016/j.catcom.2010.01.005http://dx.doi.org/10.1016/j.tet.2008.02.068http://dx.doi.org/10.1021/ol047593thttp://dx.doi.org/10.1002/anie.201101550http://dx.doi.org/10.1021/ol301249nhttp://dx.doi.org/10.1002/anie.200602456http://dx.doi.org/10.1016/j.catcom.2013.06.009http://dx.doi.org/10.1016/j.molcata.2010.11.009http://dx.doi.org/10.1016/j.catcom.2013.09.029http://dx.doi.org/10.1016/j.catcom.2012.11.028http://dx.doi.org/10.1016/j.inoche.2012.08.016http://dx.doi.org/10.1016/j.jhazmat.2010.01.012http://dx.doi.org/10.1021/jp206116ehttp://dx.doi.org/10.1021/ja0777584http://dx.doi.org/10.1039/c0jm01941khttp://dx.doi.org/10.1016/S0040-4020(00)00703-1http://dx.doi.org/10.1021/am100989ahttp://dx.doi.org/10.1016/j.cplett.2008.04.006http://dx.doi.org/10.1016/j.watres.2012.12.044http://dx.doi.org/10.4028/www.scientific.net/AMR.1112.221http://dx.doi.org/10.1016/j.inoche.2014.02.045http://dx.doi.org/10.1055/s-2008-1067107

MIRI et al./Turk J Chem

36. Zhang, T. Y.; Allen, M. J. Tetrahedron Lett. 1999, 40, 5813–5816.

37. Yang, Y.; Zhou, R.; Zhao, S.; Li, Q.; Zheng, X. J. Mol. Catal. A-Chem. 2003, 192, 303–306.

38. Iyer, S.; Thakur, V. V. J. Mol. Catal. A-Chem. 2000, 157, 275–278.

39. Thathagar, M. B.; Beckers, J.; Rothenberg, G. J. Am. Chem. Soc. 2002, 124, 11858–11859.

40. Shao, L.; Qi, C. Appl. Catal. A-Gen. 2013, 468, 26–31.

41. Wang, B.; Yang, P.; Ge, Z. W.; Li, C. P. Inorg. Chem. Commun. 2015, 61, 13–15.

42. Heshmatpour, F.; Abazari, R.; Balalaie, S. Tetrahedron 2012, 68, 3001–3011.

43. Fodor, A.; Hell, Z.; Pirault-Roy, L. Appl. Catal. A-Gen. 2014, 484, 39–50.

44. Kim, S. J.; Oh, S. D.; Lee, S.; Choi, S. H. J. Ind. Eng. Chem. 2008, 14, 449–456.

45. Xue, X.; Wang, J.; Mei, L.; Wang, Z.; Qi, K.; Yang, B. Colloid Surface B 2013, 103, 107–113.

46. Deng, Z.; Wei, J.; Xue, X.; Wang, J.; Chen, L. J. Porous Mat. 2001, 8, 37–42.

47. Jiang, Y.; Jiang, J.; Gao, Q.; Ruan, M.; Yu, H.; Qi, L. Nanotechnology 2008, 19, 75714–75720.

48. Kamal, A.; Srinivasulu, V.; Seshadri, B. N.; Markandeya, N.; Alarifi, A.; Shankaraiah, N. Green Chem. 2012, 14,

2513–2522.

49. Gao, Z.; Feng, Y.; Cui, F.; Hua, Z.; Zhou, J.; Zhu, Y.; Shi, J. J. Mol. Catal. A-Chem. 2011, 336, 51–57.

1246

http://dx.doi.org/10.1016/S0040-4039(99)01147-8http://dx.doi.org/10.1016/S1381-1169(02)00349-7http://dx.doi.org/10.1016/S1381-1169(00)00190-4http://dx.doi.org/10.1021/ja027716+http://dx.doi.org/10.1016/j.apcata.2013.08.010http://dx.doi.org/10.1016/j.inoche.2015.08.010http://dx.doi.org/10.1016/j.tet.2012.02.028http://dx.doi.org/10.1016/j.apcata.2014.07.002http://dx.doi.org/10.1016/j.jiec.2008.02.006http://dx.doi.org/10.1016/j.colsurfb.2012.10.013http://dx.doi.org/10.1023/A:1026570317713http://dx.doi.org/10.1088/0957-4484/19/7/075714http://dx.doi.org/10.1039/c2gc16430bhttp://dx.doi.org/10.1039/c2gc16430bhttp://dx.doi.org/10.1016/j.molcata.2010.12.009

IntroductionResults and discussionCatalyst preparation and characterizationCatalytic activity of catalysts in Mizoroki–Heck coupling reactionCatalytic activity of the copper catalyst in Suzuki–Miyaura coupling reaction

ExperimentalCatalyst preparationGeneral procedure for Heck coupling reactionGeneral procedure for Suzuki coupling reaction